Named in honor of Edward C. T. Chao, geologist with the U.S. Geological Survey. A discoverer of the high-pressure silica polymorphs coesite and stishovite at Meteor Crater, Arizona, Chao was the pioneer investigator of the shock metamorphism of rocks. He studied numerous terrestrial impact structures, including especially the Ries {see planet  (4327)} crater in Germany, and played a prominent role in demonstrating impact effects in the rocks brought back from the moon. Chao also carried out intensive studies of tektites and advanced key evidence that they are also the product of impacts. (M 18454) _ _.